1) Field of the Invention
This invention relates to an optical integrated device and an optical module suitable for use with an apparatus which includes, for example, a semiconductor optical amplifier (SOA) gate array switch.
2) Description of the Related Art
In recent years, in order to be ready for the network traffic which has been and is suddenly increasing, further increase of the capacity is required for a transmission apparatus such as a router or the like.
However, in an electric router apparatus (apparatus which exchanges and transmits data in the form of an electric signal) used at present, a limit to increase of the capacity is approached in terms of the processing speed and power consumption.
Therefore, a demand for an optical router apparatus (apparatus which exchanges and transmits data in the form of signal light) which allows further increase of the capacity is increasing.
In order to implement an optical router apparatus, a high-speed optical switch which switches signal light as it is at a high speed is required.
For example, as shown in FIG. 5, an SOA gate array switch 50 can change over an optical output thereof between on and off depending upon whether or not current is injected to a plurality of SOAs 51, and can perform switching at a high speed (on the nanosecond order). Therefore, the SOA gate array switch 50 is very promising as a high-speed optical switch.
As shown in FIG. 5, such an SOA gate array switch 50 as described above includes an SOA gate array device 52 including a plurality of SOAs 51, an optical fiber array 53, and an optical coupler 54.
Thus, by selectively injecting current only into one of the SOAs 51 in a state wherein signal light is inputted to all of the SOAs 51 of the SOA gate array device 52 (the SOA 51 to which current is applied is in an ON state), one of a plurality of input signal lights is selected and one output signal light is outputted through one of optical fibers which form the optical fiber array 53 (here, lens fiber array) and the optical coupler 54.
Incidentally, the SOA gate array device 52 is usually mounted in such a manner as described below.
First, the SOA gate array device (chip) 52 is bonded to a carrier with a junction face thereof directed upwardly.
Then, as shown in FIG. 6, electrodes of the SOAs 51 formed on the upper face of the SOA gate array device 52 and wirings formed on a wiring board 55 mounted in the proximity of a side face of the SOA gate array device 52 are electrically connected to each other by wire bonding so that current can be injected to each of the SOAs 51 which form the SOA gate array device 52.
Further, in order to optically connect an array optical waveguide which forms an optical input/output section of the SOA gate array device 52 and an external optical fiber array to each other, as shown in FIG. 6, lens arrays 56 (lens fiber arrays may be used instead) are individually mounted in the proximity of end faces of the SOA gate array device 52 on the optical input side and the optical output side, and the chip 52 and the lens arrays 56 are optically connected to each other.
It is to be noted that an example of a mounting method for an SOA gate array is disclosed, for example, in Alexis Lestra et al., “Monolithic Integration of Spot-Size Converters with 1.3-μm Lasers and 1.55-μm Polarization Insensitive Semiconductor Optical Amplifiers”, IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 3, No. 6, pp. 1429-1440, December 1997.
Meanwhile, a device structure is disclosed in K. Hamamoto et al., “Insertion-loss-free 1×4 optical switch fabricated using bandgap-energy-controlled selective MOVPE”, ELECTRONICS LETTERS, Vol, 32, No. 24, pp. 2265-2266, 21 Nov. 1996 and Japanese Patent Laid-Open No. 2000-208862 wherein an SOA gate array, an optical divider or an optical multiplexer/demultiplexer and optical waveguides are monolithically integrated on the same semiconductor substrate.
Incidentally, as described above, when an SOA gate array device is to be mounted, it is necessary to mount the lens arrays 56, for example, at a distance of 1 mm or less adjacent the opposite ends of the SOA gate array device 52 having a size of, for example, 1 mm or less in order to establish optical connection to optical fiber arrays as seen in FIG. 6. Also it is necessary to establish uniform and good optical coupling between a plurality of lenses which form the lens arrays 56.
Further, in order to inject current into the plural SOAs 51, it is necessary to electrically connect the electrodes of the SOAs 51 and the wirings formed on the wiring board 55 to each other using a plurality of wires 57 having lengths different from each other.
Such a mounting work for moduling as described above is very cumbersome.
Particularly, where the number of channels increases, it is necessary to lay a great number of wires 57 in the limited space sandwiched by the lens arrays 56 (or lens fiber arrays) mounted on the opposite ends of the device. Therefore, interference between the wires, interference between the wires 57 and the lens arrays 56, increase of the inductance caused by elongation of the wires 57 and so forth make problems.
On the other hand, if such a configuration as described in the article “Insertion-loss-free 1×4 optical switch fabricated using bandgap-energy-controlled selective MOVPE” and Japanese Patent Laid-Open No. 2000-208862 as mentioned hereinabove is adopted, then the length of the device increases and the number of optical connections (optical couplings) is decreased to 1 (1 channel) which is on one side of the device. Therefore, the space for performing wire bonding is expanded, and also interference between wires can be suppressed. Further, since the number of optical couplings is 1 on one side of the device, the work for establishing optical coupling is comparatively facilitated.
However, the subject that, where the number of channels increases, the length of wires increases and the inductance increases cannot be solved. Further, since the lengths of the wires connected to the electrodes of the SOAs are different from each other, the variation in electric characteristic (such as, for example, impedance or the like) is great. Therefore, there is another subject that, where the SOAs are driven by a common driver circuit, uniform and good optical gate characteristics and high-speed electric signal characteristics cannot be achieved.